The present invention relates to new photoactive polymers based on polyimides, polyamic acids and esters thereof and their use as orientation layers for liquid crystals and in the construction of unstructured and structured optical elements and multi-layer systems
The successful functioning of a Liquid Crystal Device relies upon the ability of the LC molecules within that device to adopt and maintain an alignment imposed upon them. Alignment of the LC molecules is achieved by use of an orientation layer which defines a direction of orientation for the LC molecules of the device with the result that the longitudinal axes of the molecules become aligned with the direction of orientation defined by the orientation layer. In addition to this directional alignment, the orientation layer is also able to impart to the LC molecules an angle of tilt so that the molecules align themselves at an angle to the surface of the orientation layer rather than lying parallel hereto.
Tilt angles of between 1xc2x0 and 15xc2x0 are usual for Nematic LCDs. Some electro-optical effects used for liquid crystal displays (LCD) however require alignment layers with very high pretilt angles. Vertically aligned nematic (VAN) LCDs for instance require pretilt angles between 85xc2x0 and 90xc2x0, measured from the surface plane. In the case of hybrid aligned nematic (HAN) LCDs, the pretilt angle at one of the substrates has to be in the above range, whereas the tilt angle at the other substrate is low (typically 0-10xc2x0).
Methods of preparing structured and unstructured orientation layers are well known to a skilled person. Customarily used uniaxially rubbed polymer orientation layers such as, for example, polyimides however impact a series of disadvantages like dust generation during rubbing process, destruction of thin film transistors and lack of structuring. The rubbing process consequently does not allow the production of structured layers Orientation layers in which the direction of orientation can be predetermined by irradiation with polarised light have been known for some time. It is by that means possible to avoid the problems inherent in the rubbing process In addition, it is possible to provide areas having different orientation and thus to structure the orientation layer as described for example in Jpn. J. Appl. Phys. 31 (1992), 2155-64 (Schadt et al.). In that process the dimerisation of polymer-bonded photoreactive cinnamic acid groups induced by irradiation with linearly polarised light is employed leading to an anisotropic polymer network. Those photo-oriented polymer networks can be used wherever structured or unstructured liquid crystal orientation layers are required. In addition to their use in LCDs, such orientation layers can also be used, for example, in the production of so-called hybrid layers as exemplified in European Patent Applications EP-A-0611981, EP-A-0689084 and EP-A-0753785 (all F. Hoffmann-La Roche A G). Using those hybrid layers of photostructured orientation polymers and crosslinkable low molecular weight liquid crystals it is possible to realise optical elements such as, for example, non-absorptive colour filters, linear and circular polarisers, optical delay layers and so on.
EP-A-0611786 and WO-A-96/10049 (both F. Hoffmann-La Roche A G) as well as EP-A-0763552 (Rolic A G), describe cinnamic acid polymers that are suitable in principle for the synthesis of such anisotropically crosslinked, photostructured orientation layers for liquid crystals. In the case of the compounds described in EP-A-0763552 and WO-A-96/10049, on irradiation with linearly polarised light it is possible, in addition to inducing the desired orientation, simultaneously to induce an angle of tilt. It is thus possible to produce layers having structuring in respect of surface orientation and angle of tilt.
The above photostructured orientation layers have the disadvantage, however, that for certain applications, especially for use in TFT displays, they result in adjacent liquid crystal mixture having an insufficient electrical resistance value. In TFT displays, too low a resistance value of the liquid crystal medium leads to an inadequate xe2x80x9cholding ratioxe2x80x9d, which is a measure of the voltage drop in the display after the voltage has been switched off. Low holding ratio values, however, bring about undesirable changes in brightness and contrast over time and thus result in unstable graduations of the grey tones.
Recently photoreactive materials for orientation layers with improved holding ratios were described in WO-A-99/49360 (Rolic A G), JP-A-10-195296, JP-A-10-232400 (both Samsung Electron Devices Co., Ltd), WO-A-99/15576 (Rolic AG) and WO-A-99/51662 (Kanegafuchi Kagaku Kogyo K K). In WO-A-99/49360, JP-A-10-195296 and JP-A-10-232400 blends of polymeric compounds containing photoreactive polymers on the one hand and polyimides on the other hand are proposed. A disadvantage of such blends is their limited miscibility. Low contents of photoreactive polymers however lead to a loss of orienting properties and consequently to a reduced contrast ratio of liquid crystal layers to be oriented whereas a reduced polyimide content results in insufficient holding ratios. In WO-A-99/15576 and WO-A-99/51662 polyimides incorporating photoreactive cinnamate groups in their side chains are described. WO-A-99/15576 discloses photoactive polymers which contain as side-chains photocrosslinkable groups of the following formula: 
A typical monomer unit is 3,5-diaminobenzoic acid 6-[2-methoxy-4-(2-methoxycarbonylvinyl)phenoxy]hexyl ester: 
The cinnamic acid derivatives disclosed in WO-A-99/15576 are linked to the polyimide backbone such that the photoreactive groups are pointing away from the backbone.
WO-A-99/51662 discloses photoactive polymers having a cinnamic skeletal structure. A typical monomer disclosed is of the following formula: 
The polyimide compositions are said to combine the photoreactivity and thermal reactivity characteristic of the cinnamic acid skeletal structure. There is no teaching of the improvement of the orientation of liquid crystals.
Consequently stable photoalignable materials for high pretilt angles with sufficiently high holding ratios are not known so far. The problem underlying the invention was, therefore, to find photoreactive polymers that, when irradiated with polarised light, result in the production of stable, high-resolution orientation patterns having very high angle of tilt and at the same time result in sufficiently high holding ratios in the adjacent liquid crystal medium.
Surprisingly, it has now been found that polyimides, incorporating cinnamic acid derivatives in their side chains in such a way, that the cinnamic acid groups are linked to the polyimide backbone via the carboxylic group by means of a flexible spacer, perfectly fulfil the above requirements. The illumination of those compounds, using linearly polarised light, results in excellent orientation of the liquid crystals, in a sufficiently high holding ratio of the liquid crystal medium and simultaneously in an appreciable increase of the tilt angle up to 90xc2x0.
A first aspect of the present invention therefore provides photoactive polymers from the class of polyimides polyamide acids and esters thereof, characterised in that they comprise as side-chains photocrosslinkable groups of the general formula I: 
wherein the broken line indicates the point of linkage to the polyimide main chain and wherein:
A represents pyrimidine-2,5-diyl, pyridine-2,5-diyl, 2,5-thiophenylene, 2,5-furanylene, 1,4- or 2,6-naphthylene, or phenylene; which is optionally substituted by a group selected from fluorine, chlorine, cyano or by a C1-18 cyclic, straight-chain or branched alkyl residue, which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent alkyl xe2x80x94CH2xe2x80x94 groups are optionally replaced by a group Q;
B is a straight-chain or branched alkyl residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 3 to 18 carbon atoms, wherein one or more non-adjacent CH2 groups may independently be replaced by a group Q;
C1 and C2 each independently of the other represents an aromatic or alicyclic group which is unsubstituted or substituted by fluorine, chlorine, cyano, or by a cyclic, straight-chain or branched alkyl residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 1 to 18 carbon atoms and wherein one or more non-adjacent CH2 groups may independently be replaced by a group Q;
D represents an oxygen atom or xe2x80x94NR1xe2x80x94 wherein R1 represents a hydrogen atom or lower alkyl;
S1 and S2 each independently of the other represent a single covalent bond or a spacer unit, such as a straight-chain or branched alkylene residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 1 to 24 carbon atoms, wherein one or more non-adjacent CH2 groups may independently be replaced by a group Q;
S3 represents a spacer unit, such as a straight-chain or branched alkylene residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 2 to 24 carbon atoms, wherein one or more non-adjacent CH2 groups may independently be replaced by an aromatic, an alicyclic group or a group Q;
Q represents a group selected from xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94Si(CH3)2xe2x80x94Oxe2x80x94Si(CH3)2xe2x80x94, xe2x80x94NR1xe2x80x94, xe2x80x94NR1xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94NR1xe2x80x94, xe2x80x94NR1xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94NR1xe2x80x94, xe2x80x94NR1xe2x80x94COxe2x80x94NR1 xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94 and xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94, wherein R1 represents a hydrogen atom or lower alkyl;
n1 and n2 are each independently 0 or 1; and
X, Y each independently of the other represents hydrogen, fluorine, chlorine, cyano, alkyl optionally substituted by fluorine having from 1 to 12 carbon atoms in which optionally one or more non-adjacent CH2 groups are replaced by xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94 and/or xe2x80x94CHxe2x95x90CHxe2x80x94.
By the term xe2x80x9caromaticxe2x80x9d it should be understood to include optionally substituted carbocylic and heterocyclic groups incorporating five, six or ten ring atoms like furan, phenyl, pyridine, pyrimidine, naphthalene, or tetraline units.
By the term xe2x80x9ccyclic, straight-chain or branched alkyl group, which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent xe2x80x94CH2xe2x80x94 groups are optionally replaced by a group Qxe2x80x9d it should be understood to include groups selected from the group comprising methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, 3-methylpentyl, allyl, but-3-en-1-yl, pent4-en-1-yl, hex-5-en-1-yl, propynyl, butynyl, pentynyl, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, isopentyloxy, cyclopentyloxy, hexyloxy, cyclohexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, 3-methylpentyloxy, allyloxy, but-3-enyloxy, pent-4-enyloxy, cyclohexylmethoxy, cyclopentylmethoxy, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonyl, sec-butoxycarbonyl, tert-butoxycarbonyl, pentyloxycarbonyl, isopentyloxycarbonyl, cyclopentyloxycarbonyl, hexyloxycarbonyl, cyclohexyloxycarbonyl, octyloxycarbonyl, nonyloxycarbonyl, decyloxycarbonyl, undecyloxycarbonyl, dodecyloxycarbonyl, 3-methylpentyloxycarbonyl, allyloxycarbonyl, but-3-enyloxycarbonyl, pent4-enyloxycarbonyl, cylohexylmethoxycarbonyl, cyclopentylmethoxycarbonyl, acetoxy, ethylcarbonyloxy, propylcarbonyloxy, isopropylcarbonyloxy, butylcarbonyloxy, isobutylcarbonyloxy, sec-butylcarbonyloxy, tert-butylcarbonyloxy, pentylcarbonyloxy, isopentylcarbonyloxy, cyclopentylcarbonyloxy, hexylcarbonyloxy, cyclohexylcarbonyloxy, octylcarbonyloxy, nonylcarbonyloxy, decylcarbonyloxy, undecylcarbonyloxy, dodecylcarbonyloxy, 3-methylpentylcarbonyloxy, but-3-enyloxy, pent-4-enyloxy, acetyl, ethylcarbonyl, propylcarbonyl, isopropylcarbonyl, butylcarbonyl, isobutylcarbonyl, sec-butylcarbonyl, pentylcarbonyl, isopentylcarbonyl, cyclohexylcarbonyl, octylcarbonyl, nonylcarbonyl, decylcarbonyl undecylcarbonyl, dodecylcarbonyl, methoxyacetoxy, 1-methoxy-2-propoxy, 3-methoxy-1-propoxy, 2-methoxyethoxy, 2-isopropoxyethoxy, 1-ethoxy-3-pentyloxy, 3-butynyloxy, 4-pentynyloxy, 5-chloropentynyl, 4-pentynecarbonyloxy, 6-propyloxyhexyl, 6-propyloxyhexyloxy, 2-fluoroethyl, trifluoromethyl, 2,2,2-trifluoroethyl, 1H,1H-pentadecafluorooctyl, 1H, 1H,7H-dodecafluoroheptyl, 2-(perfluorooctyl)ethyl, 2-(perfluorobutyl)ethyl, 2-(perfluorohexyl)ethyl, 2-(perfluorodecyl)ethyl, perfluoropropyl, perfluorobutyl, perfluoroheptyl, perfluorooctyl, perfluorononyl, 1-fluoropropoxy, 1-fluoropentyloxy, 2-fluoropropoxy, 2,2-difluoropropoxy, 3-fluoropropoxy, 3,3-difluoropropoxy, 3,3,3-trifluoropropoxy, trifluoromethoxy and the like.
By the term xe2x80x9clower alkylxe2x80x9d it should be understood to include straight chain and branched hydrocarbon radicals having from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms. Methyl, ethyl, propyl and isopropyl groups are especially preferred.
By the term xe2x80x9calicyclicxe2x80x9d it should be understood to include non-aromatic carbocyclic or heterocyclic ring systems with 3 to 10 carbon atoms like cyclopropane, cyclobutane, cyclopentane, cyclopentene, cyclohexane, cyclohexene, cyclohexadiene and decaline.
It is also preferred that the group A is selected from pyrimidine-2,5-diyl, pyridine-2,5-diyl, 2,5-thiophenylene, 2,5-furanylene, 1,4- or 2,6-naphthylene and a phenylene group, which is optionally substituted by a C1-12 cyclic, straight-chain or branched alkyl residue, which alkyl group is optionally substituted by one or more halogen atoms and in which one or more non-adjacent alkyl xe2x80x94CH2xe2x80x94 groups are independently optionally replaced by a group selected from xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94 and xe2x80x94Cxe2x89xa1Cxe2x80x94.
It is especially preferred that A is selected from phenylene, which is optionally substituted by a C1-12 straight-chain or branched alkyl residue, which alkyl group is substituted by one or more fluorine atoms, and wherein one or more non-adjacent alkyl xe2x80x94CH2xe2x80x94 groups are independently optionally replaced by a group selected from xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94 and xe2x80x94CHxe2x95x90CHxe2x80x94.
By the term xe2x80x9cphenylenexe2x80x9d it should be understood to include 1,2-, 1,3- or 1,4-phenylene, which is optionally substituted. It is preferred that the phenylene group is either a 1,3- or a 1,4-phenylene.
Preferred groups B are selected from straight-chain or branched alkyl residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 3 to 18 carbon atoms, wherein one or more CH2 groups may independently be replaced by xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94, with the proviso that oxygen atoms are not directly attached to each other.
It is especially preferred that B is selected from straight-chain or branched alkyl residue which is unsubstituted, mono-substituted or poly-substituted by halogeno, having 3 to 12 carbon atoms, wherein one or more CH2 groups may independently be replaced by xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, with the proviso that oxygen atoms are not directly attached to each other.
It is preferred that each of the groups C1 and C2 are selected from cyclohexane-1,4-diyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl, 1,4- or 2,6-naphthylene and phenylene, which is optionally substituted by one or more groups selected from fluorine, chlorine, cyano and a C1-12 cyclic, straight-chain or branched alkyl residue, which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent alkyl xe2x80x94CH2xe2x80x94 groups are optionally independently replaced by a group selected from xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94 and xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94.
It is especially preferred that the groups C1 and C2 are selected from cyclohexane-1,4-diyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl, 2,6-naphthylene and phenylene, which is optionally substituted by one or more fluorine atoms or a C1-8 straight-chain or branched alkyl residue, which is optionally substituted by one or more fluorine atoms, and in which one or more non-adjacent alkyl xe2x80x94CH2xe2x80x94 groups are independently optionally replaced by a group selected from xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94 and xe2x80x94CHxe2x95x90CHxe2x80x94.
Preferred groups D are oxygen atom or xe2x80x94NHxe2x80x94.
It is especially preferred that D is an oxygen atom.
It is preferred that the groups S1 and S2 are selected from a single covalent bond, xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94NR1xe2x80x94, xe2x80x94NR1xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94NR1xe2x80x94, xe2x80x94NR1xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94NR1xe2x80x94, xe2x80x94NR1xe2x80x94COxe2x80x94NR1xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94 and a straight-chain or branched alkylene group, in which two or three non-adjacent alkylene xe2x80x94CH2xe2x80x94 group are independently optionally replaced by a group Q with the proviso the total number of chain carbon atoms in the alkylene group does not exceed 24, wherein R1 represents a hydrogen atom or lower alkyl.
It is more preferred that S1 and S2 are selected from a single covalent bond, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94(CH2)r xe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94NR1xe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94, xe2x80x94NR1xe2x80x94COxe2x80x94(CH2)rxe2x80x94, xe2x80x94COxe2x80x94NR1xe2x80x94(CH2)rxe2x80x94, xe2x80x94NR1xe2x80x94(CH2)rxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94COxe2x80x94NR1xe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94, xe2x80x94NR1xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94NR1xe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94NR1xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94, xe2x80x94NR1(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94NR1xe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94NR1xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94, xe2x80x94COxe2x80x94NR1xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94NR2xe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94COxe2x80x94NR1xe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94 and xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, wherein R1 is as defined above, r and s each represent an integer from 1 to 20, preferably from 1 to 12, and r+sxe2x89xa621, preferably xe2x89xa615.
By the terms xe2x80x94(CH2)rxe2x80x94 and xe2x80x94(CH2)sxe2x80x94 it should be understood to include straight-chain or branched alkylene groupings containing r or s carbon atoms respectively.
It is especially preferred that S1 and S2 are selected from a single covalent bond, xe2x80x94(CH2)rxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94NHxe2x80x94, xe2x80x94(CH2)rxe2x80x94NHxe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94, xe2x80x94COxe2x80x94NHxe2x80x94(CH2)rxe2x80x94, xe2x80x94NHxe2x80x94COxe2x80x94(CH2)rxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94O(CH2)rxe2x80x94COxe2x80x94NHxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NHxe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94NHxe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94NHxe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94NHxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94NHxe2x80x94COxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94NHxe2x80x94COxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NHxe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NHxe2x80x94COxe2x80x94(CH2)sxe2x80x94Oxe2x80x94 and xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94NHxe2x80x94COxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, wherein r and s each represent an integer from 1 to 12 and r+sxe2x89xa615.
Examples of preferred groups S1 and S2 include 1,2-ethylene, 1,3-propylene, 1,4-butylene, 1,5-pentylene, 1,6-hexylene, 1,7-heptylene, 1,8-octylene, 1,9-nonylene, 1,10-decylene, 1,11-undecylene, 1,12-dodecylene, 3-methyl-1,4-butylene, methyleneoxy, 2-ethyleneoxy, 3-propyleneoxy, 3-propyleneoxycarbonyl, 2-ethylenecarbonyloxy, 4-butyleneoxy, 4-butyleneoxycarbonyl, 3-propylenecarbonyloxy, 5-pentyleneoxy, 5-pentyleneoxycarbonyl, 4-butylenecarbonyloxy, 6-hexyleneoxy, 6-hexyleneoxycarbonyl, 5-pentylenecarbonyloxy, 7-heptyleneoxy, 7-heptyleneoxycarbonyl, 6-hexylenecarbonyloxy, 8-octyleneoxy, 8-octyleneoxycarbonyl, 7-heptylenecarbonyloxy, 9-nonyleneoxy, 9-nonyleneoxycarbonyl, 8-octylenecarbonyloxy, 10-decyleneoxy, 10-decyleneoxycarbonyl, 9-nonylenecarbonyloxy, 11-undecyleneoxy, 11-undecyleneoxycarbonyl, 10-decylenecarbonyloxy, 12-dodecyleneoxy, 12-dodecyleneoxycarbonyl, 11-undecylenecarbonyloxy, 3-propyleneiminocarbonyl, 4-butyleneiminocarbonyl, 5-pentyleneiminocarbonyl, 6-hexyleneiminocarbonyl, 7-heptyleneiminocarbonyl, 8-octyleneiminocarbonyl, 9-nonyleneiminocarbonyl, 10-decyleneiminocarbonyl, 11-undecyleneiminocarbonyl, 12-dodecyleneiminocarbonyl, 2-ethylenecarbonylimino, 3-propylenecarbonylimino, 4-butylenecarbonylimino, 5-pentylenecarbonylimino, 6-hexylenecarbonylimino, 7-heptylenecarbonylimino, 8-octylenecarbonylimino, 9-nonylenecarbonylimino, 10-decylenecarbonylimino, 1-undecylenecarbonylimino, 6-(3-propyleneiminocarbonyloxy)hexylene, 6-(3-propyleneoxy)hexylene, 6-(3-propyleneoxy)hexyleneoxy, 6-(3-propyleneiminocarbonyloxy)hexyleneoxy, 6-(3-propyleneiminocarbonyl)hexyl, 6-(3-propyleneiminocarbonyl)hexyloxy, 1,2-ethylenedioxy, 1,3-propylenedioxy, 1,4-butylenedioxy, 1,5-pentylenedioxy, 1,6-hexylenedioxy, 1,7-heptylenedioxy, 1,8-octylenedioxy, 1,9-nonylenedioxy, 1,10-decylenedioxy, 1,11-undecylenedioxy, 1,12-dodecylenedioxy and the like.
It is preferred that the group S3 is selected from a spacer unit, such as a straight-chain or branched alkylene residue having 5 to 24 carbon atoms, wherein one or more non-adjacent CH2 groups may independently be replaced by a group Q. More preferably the group S3 has 6 to 24 carbon atoms, and especially 7 to 20 carbon atoms, wherein one or more non-adjacent CH2 groups may independently be replaced by a group Q. Note that, when the polyimide main chain includes an aromatic ring linking the polymerisable groups, the ring is to be regarded as part of the main chain and not to be regarded as part of the spacer.
It is more preferred that S3 is selected from xe2x80x94(CH2)r-1xe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94, xe2x80x94NR1xe2x80x94COxe2x80x94(CH2)rxe2x80x94, xe2x80x94COxe2x80x94NR1xe2x80x94(CH2)rxe2x80x94, xe2x80x94NR1xe2x80x94(CH2)rxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94 and xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, wherein R1 is as defined above, r and s each represent an integer from 1 to 20, preferably from 2 to 12, and r+s less than 21, preferably  less than 15.
Examples of preferred group S3 are 1,2-ethylene, 1,3-propylene, 1,4-butylene, 1,5-pentylene, 1,6-hexylene, 1,7-heptylene, 1,8-octylene, 1,9-nonylene, 1,10-decylene, 1,11-undecylene, 1,12-dodecylene, 3-methyl-1,4-butylene, 2-oxyethylene, 3-oxypropylene, 4-oxybutylene, 5-oxypentylene, 6-oxyhexylene, 7-oxyheptylene, 8-oxyoctylene, 9-oxynonylene, 10-oxydecylene, 11-oxyundecylene, 12-oxydodecylene, 2-(oxycarbonyl)ethylene, 3-(oxycarbonyl)propylene, 4-(oxycarbonyl)butylene, 5-(oxycarbonyl)pentylene, 6-(oxycarbonyl)hexylene, 7-(oxycarbonyl)heptylene, 8-(oxycarbonyl)octylene, 9-(oxycarbonyl)nonylene, 10-(oxycarbonyl)decylene, 11-(oxycarbonyl)undecylene, 12-(oxycarbonyl)dodecylene, 2-(carbonyloxy)ethylene, 3-(carbonyloxy)propylene, 4-(carbonyloxy)butylene, 5-(carbonyloxy)pentylene, 6-(carbonyloxy)hexylene, 7-(carbonyloxy)heptylene, 8-(carbonyloxy)octylene, 9-(carbonyloxy)nonylene, 10-(carbonyloxy)decylene, 11-(carbonyloxy)undecylene, 12-(carbonyloxy)dodecylene, 2-(carbonylimino)ethyiene, 3-(carbonylimino)propylene, 4-(carbonylimino)butylene, 5-(carbonylimino)pentylene, 6-(carbonylimino)hexylene, 7-(carbonylimino)-heptylene, 8-(carbonylimino)octylene, 9-(carbonylimino)nonylene, 10-(carbonylimino)decylene, 11-(carbonylimino)undecylene, 12-(carbonylimino)dodecylene, 2-iminoethylene, 3-iminopropylene, 4-iminobutylene, 5-iminopentylene, 6-iminohexylene, 7-iminoheptylene, 8-iminooctylene, 9-iminononylene, I 0-iminodecylene, 11-iminoundecylene, 12-iminododecylene, 2-iminocarbonylethylene 3-iminocarbonylpropylene, 4-iminocarbonylbutylene, 5-iminocarbonylpentylene. 6-iminocarbonylhexylene, 7-iminocarbonylheptylene, 8-iminocarbonyloctylene, 9-iminocarbonylnonylene, 10-iminocarbonyldecylene, 1-iminocarbonylundecylene, 12-iminocarbonyldodecylene, 2-(2-ethyleneoxy)ethylene, 2-(3-propyleneoxy)ethylene, 6-(4-butyleneoxy)hexylene, 2-(2-ethyleneiminocarbonyl)ethylene, 2-(3-propyleneiminocarbonyl)ethylene, 6-(4-butyleneiminocarbonyl)hexylene, 6-(3-propyleneiminocarbonyloxy)hexylene, 6-(3-propyleneiminocarbonyl)hexylene and the like.
It is preferred that the groups X and Y represent hydrogen.
It is preferred that n1+n2=0 or 1, and especially preferred that n1=n2=0.
Preferred monomer units from which the main chains of the side-chain polymers according to the invention are built up, are the imide groups of the general formulae II, IV and VI and/or the analogous amic acid groups and amic acid ester groups of the general formulae III, V and VII; especially preferred are the groups of the formulae II, III, VI and VII: 
wherein:
the broken line symbolises the linkage to S3 
T1 represents a tetravalent organic radical;
T2, T3 each independently represent a trivalent aromatic or alicyclic group which is optionally substituted by a group selected from fluorine, chlorine, cyano and a C1-18 cyclic, straight-chain or branched alkyl residue, which is optionally substituted by one or more halogen groups and in which one or more non-adjacent alkyl xe2x80x94CH2xe2x80x94 groups are independently optionally replaced by a group selected from xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94 and xe2x80x94Cxe2x80x94;
S4 to S8 are each independently selected from a single covalent bond and a C1-24 straight-chain or branched alkylene residue, which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent alkylene xe2x80x94CH2xe2x80x94 groups are, independently, optionally replaced by a group Q;
E is selected from the group comprising a nitrogen atom, a group xe2x80x94CR1xe2x80x94 and an aromatic or alicyclic divalent, trivalent or tetravalent group, which is optionally substituted by one or more groups selected from fluoro, chloro, cyano and a C1-18 cyclic, straight-chain or branched alkyl residue which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent xe2x80x94CH2xe2x80x94 groups are, independently optionally, replaced by a group selected from xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94 and xe2x80x94Cxe2x80x94Cxe2x80x94, wherein R1 is as defined above;
F represents an aliphatic, alicyclic or aromatic divalent radical; and
G represents a hydrogen atom or a monovalent organic group.
By the term xe2x80x9caliphaticxe2x80x9d it should be understood to include saturated and unsaturated, straight-chain and branched alkyl groups, which may be optionally substituted and in which one or more non-adjacent xe2x80x94CH2xe2x80x94 groups are replaced by one or more heteroatoms. Optional substituents include alkyl, aryl, cycloalkyl, amino, cyano, epoxy, halogen, hydroxy, nitro and oxo. Examples of heteroatoms that can replace the one or more xe2x80x94CH2xe2x80x94 groups include nitrogen, oxygen and sulfur. Replacement nitrogen atoms may be further substituted with groups such as alkyl, aryl and cycloalkyl.
The tetravalent organic radical T1 is preferably derived from an aliphatic, alicyclic or aromatic tetracarboxylic acid dianhydride. Alicyclic or aliphatic tetracarboxylic acid anhydrides are preferably selected from 1,1,4,4-butanetetracarboxylic acid dianhydride, ethylenemaleic acid dianhydride, 1,2,3,4-cyclobutanetetracarboxylic acid cianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 3,5,6-tricarboxynorbornylacetic acid diannydride, 2,3,4,5-tetrahydrofiurantetracarboxylic acid dianhydride, 4-(2, 5-dioxotetrahydrofuran-3-yl)tetrahydronaphthalene-1,2-dicarboxylic acid dianhydride 5-(2,5-dioxotetrahydrofuran-3-yl)-3-methyl-3-cyclo-hexene-1,2-dicarboxylic acid dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic acid dianhydride and 1,8-dimethylbicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride.
Aromatic tetracarboxylic acid dianhydrides are preferably selected from pyromellitic acid dianhydride, 3,3xe2x80x2,4,4xe2x80x2-benzophenonetetracarboxylic acid dianhydride, 4,4xe2x80x2-oxydiphthatic acid dianhydride, 3,3xe2x80x2,4,4xe2x80x2-diphenylsulfoneteracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 3,3xe2x80x2,4,4xe2x80x2-dimethyldiphenylsilanetetracarboxylic acid dianhydride, 3,3xe2x80x2,4,4xe2x80x2-tetraphenylsilanetetracarboxylic acid dianhydride, 1,2,3,4-furantetracarboxylic acid dianhydride, 4,4xe2x80x2-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride, 4,4xe2x80x2-bis(3,4-dicarboxyphenoxy)diphenyl sulfone dianhydride, 4,4xe2x80x2-bis(3,4-dicarboxyphenoxy)diphenylpropane dianhydride, 3,3xe2x80x2,4,4xe2x80x2-biphenyltetracarboxylic acid dianhydride, ethylene glycol bis(trimellitic acid)dianhydride, 4,4xe2x80x2-(1,4-phenylene)bis(phthalic acid)dianhydride, 4,4xe2x80x2-(1,xe2x80x23-phenylene)bis(phthalic acid)dianhydiride, 4,4xe2x80x2-(hexafluoroisopropylidene)diphthalic acid dianhydride, 4,4xe2x80x2-oxydi(1,4-phenylene)bis(phthalic acid)dianhydride and 4,4xe2x80x2-methylenedi(1,4-phenylene)bis(phthalic acid)dianhydride.
It is especially preferred that the tetracarboxylic acid dianhydrides used to form the tetravalent organic radical T1 are selected from 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 5-(2,5-dioxotetrahydrofuran-3-yl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid dianhydride, 4-(2,5-dioxotetrabydrofuran-3-yl)tetrahydronapthalene-1,2-dicarboxylic acid dianhydride, 4,4xe2x80x2-(hexafluoroisopropylidene)diphthalic acid dianhydride and bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride.
Each of the groups T2 and T3 can be derived from an aliphatic, alicyclic or aromatic dicarboxylic acid anhydride.
The groups T2 and T3 are preferably trivalent aromatic or alicyclic groups, the three valencies of which are distributed between three different carbon atoms, with the proviso that two of the valencies are located at adjacent carbon atoms. It is especially preferred that the groups T2 and T3 are trivalent benzene derivatives.
The group S4 is preferably selected from a single covalent bond, xe2x80x94(CH2)rxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94NR1xe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94(CH2)sxe2x80x94COxe2x80x94Oxe2x80x94 and xe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94COxe2x80x94, wherein R1 is as defined herein above; r and s each represent an integer from 1 to 20, and r+sxe2x89xa621. It is more preferred that r and s each represent an integer from 2 to 12. It is especially preferred that r+sxe2x89xa615.
Examples of preferred groups S4 include 1,2-ethylene, 1,3-propylene, 1,4-butylene, 1,5-pentylene, 1,6-hexylene, 1,7-heptylene, 1,8-octylene, 1,9-nonylene, 1,10-decylene, 1,11-undecylene, 1,12-dodecylene, 3-methyl-1,4-butylene, 3-propyleneoxy, 3-propyleneoxycarbonyl, 2-ethylenecarbonyloxy, 4-butyleneoxy, 4-butyleneoxycarbonyl, 3-propylenecarbonyloxy, 5-pentyleneoxy, 5-pentyleneoxycarbonyl, 4-butylenecarbonyloxy, 6-hexyleneoxy, 6-hexyleneoxycarbonyl, 5-pentylenecarbonyloxy, 7-heptyleneoxy, 7-heptyleneoxycarbonyl, 6-hexylenecarbonyloxy, 8-octyleneoxy 8-octyleneoxycarbonyl, 7-heptylenecarbonyloxy, 9-nonyleneoxy, 9-nonyleneoxycarbonyl, 8-octylenecarbonyloxy, 1 0-decyleneoxy, 10-decyleneoxycarbonyl, 9-nonylenecarbonyloxy, 11-undecyleneoxy, 1-undecyleneoxycarbonyl, 10-decylenecarbonyloxy, 12-dodecyleneoxy, 12-dodecyleneoxycarbonyl, 11-undecylenecarbonyloxy, 3-propyleneiminocarbonyl, 4-butyleneiminocarbonyl, 5-pentyleneininocarbonyl, 6-hexyleneiminocarbonyl, 7-heptyleneiminocarbonyl, 8-octyleneimnocarbonyl, 9-nonyleneiminocarbonyl, 10-decyleneiminocarbonyl, 11-undecyleneiminocarbonyl, 12-dodecyleneiminocarbonyl, 2-ethylenecarbonylimino, 3-propylenecarbonylimino, 4-butylenecarbonylimino, 5-pentylenecarbonylimino, 6-hexylenecarbonylimino, 7-heptylenecarbonylimino, 8-octylenecarbonylimino, 9-nonylenecarbonylimino, 10-decylenecarbonylimino, 11-undecylenecarbonylimino 6-(3-propyleneiminocarbonyloxy)hexylene, 6-(3-propyleneoxy)hexylene, 6-(3-propyleneoxy)hexyleneoxy, 6-(3-propyleneiminocarbonyloxy)hexyleneoxy, 6-(3-propyleneiminocarbonyl)hexylene, 6-(3-propyleneiminocarbonyl)hexyleneoxy and the like.
The groups S5 and S8 are preferably selected from a single bond, xe2x80x94(CH2)rxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94, xe2x80x94COxe2x80x94(CH2)rxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94, xe2x80x94NR1xe2x80x94COxe2x80x94(CH2)rxe2x80x94, xe2x80x94NR1xe2x80x94(CH2)rxe2x80x94, xe2x80x94COxe2x80x94NR1xe2x80x94(CH2)rxe2x80x94, xe2x80x94NR1xe2x80x94COxe2x80x94(CH2)rxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rNR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94 and xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, wherein R1 is defined as herein above; r and s each represent an integer from 1 to 20; and r+sxe2x89xa621. It is more preferred that r and s each represent an integer from 2 to 12. It is further preferred that r+sxe2x89xa615.
Examples of preferred groups S5 and S8 include 1,2-ethylene, 1,3-propylene, 1,4-butylene, 1,5-pentylene, 1,6-hexylene, 1,7-heptylene, 1,8-octylene, 1,9-nonylene, 1,10-decylene, 1,11-undecylene, 1,12-dodecylene, 3-methyl-1,4-butylene, 2-oxyethylene, 3-oxypropylene, 4-oxybutylene, 5-oxypentylene, 6-oxyhexylene, 7-oxyheptylene, 8-oxyoctylene, 9-oxynonylene, 10-oxydecylene, 11-oxyundecylene, 12-oxydodecylene, 2-(oxycarbonyl)ethylene, 3-(oxycarbonyl)propylene, 4-(oxycarbonyl)butylene, 5-(oxycarbonyl)pentylene, 6-(oxycarbonyl)hexylene, 7-(oxycarbonyl)heptylene, 8-(oxycarbonyl)octylene, 9-(oxycarbonyl)nonylene, 10-(oxycarbonyl)decylene, 11-(oxycarbonyl)undecylene, 12-(oxycarbonyl)dodecylene, 2-(carbonyloxy)ethylene, 3-(carbonyloxy)propylene, 4-(carbonyloxy)butylene, 5-(carbonyloxy)pentylene, 6-(carbonyloxy)hexylene, 7-(carbonyloxy)heptylene, 8-(carbonyloxy)octylene, 9-(carbonyloxy)nonylene, 10-(carbonyloxy)decylene, 11-(carbonyloxy)undecylene, 12-(carbonyloxy)dodecylene, 2-(carbonylimino)ethylene, 3-(carbonylimino)propylene, 4-(carbonylimino)butylene, 5-(carbonylimino)pentylene. 6-(carbonylimino)hexylene, 7-(carbonylimino)heptylene, 8-(carbonylimino)octylene, 9-(carbonylimino)nonylene, 10-(carbonylimino)decylene, 11-(carbonylimino)undecylene, 12-(carbonylimino)dodecylene, 2-iminoethylene, 3-iminopropylene, 4-iminobutylene, 5-iminopentylene, 6-iminohexylene, 7-iminoheptylene, 8-iminooctylene, 9-iminononylene, 10-iminodecylene, 11-iminoundecylene, 12-iminododecylene, 2-iminocarbonylethylene, 3-iminocarbonylpropylene, 4-iminocarbonylbutylene, 5-iminocarbonylpentylene, 6-iminocarbonylhexylene, 7-iminocarbonylheptylene, 8-iminocarbonyloctylene, 9-iminocarbonylnonylene, 10-iminocarbonyldecylene, I 1-iminocarbonylundecyiene, 12-iminocarbonyldodecylene, 2-(2-ethyleneoxy)ethylene, 2-(3-propyleneoxy)ethylene, 6-(4-butyleneoxy)hexylene, 2-(2-ethyleneiminocarbonyl)ethylene, 2-(3-propyleneiminocarbonyl)ethylene, 6-(4-butyleneiminocarbonyl)hexylene, 6-(3-propyleneiminocarbonyloxy)hexylene, 6-(3-propyleneiminocarbonyl)hexylene and the like.
The groups S6 and S7 are preferably selected from a single bond, xe2x80x94(CH2)rxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94NR1xe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94, xe2x80x94NR1xe2x80x94COxe2x80x94(CH2)rxe2x80x94, xe2x80x94CO xe2x80x94NR1xe2x80x94(CH2)rxe2x80x94, xe2x80x94NR1(CH2)rxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94COxe2x80x94NR1xe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94, xe2x80x94NR1xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94NR1xe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94NR1xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94, xe2x80x94NR1xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94NR1xe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94NR1xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94, xe2x80x94COxe2x80x94NR1xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94CO(CH2)rxe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94COxe2x80x94NR1xe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rNR1xe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94Oxe2x80x94COxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94(CH2)rxe2x80x94NR1COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94,xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94(CH2)rxe2x80x94NR1xe2x80x94COxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94, xe2x80x94(CH2)sxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94(CH2)rxe2x80x94Oxe2x80x94(CH2)sxe2x80x94Oxe2x80x94, wherein R1 is defined as herein above; r and s each represent an integer from 1 to 20; and r+sxe2x89xa621. It is more preferred that r and s each represent an integer from 2 to 12. It is especially preferred that r+sxe2x89xa615.
Examples of preferred groups S6 and S7 include 1,2-ethylene, 1,3-propylene, 1,4-butylene, 1,5-pentylene, 1,6-hexylene, 1,7-heptylene, 1,8-octylene, 1,9-nonylene, 1,10-decylene, 1,11-undecylene, 1,12-dodecylene, 3-methyl-1,4-butylene, 3-propyleneoxy, 3-propyleneoxycarbonyl, 2-ethylenecarbonyloxy, 4-butyleneoxy, 4-butyleneoxycarbonyl, 3-propylenecarbonyloxy, 5-pentyleneoxy, 5-pentyleneoxycarbonyl, 4-butylenecarbonyloxy, 6-hexyleneoxy, 6-hexyleneoxycarbonyl, 5-pentylenecarbonyloxy, 7-heptyleneoxy, 7-heptyleneoxycarbonyl, 6-hexylenecarbonyloxy, 8-octyleneoxy 8-octyleneoxycarbonyl, 7-heptylenecarbonyloxy, 9-nonyleneoxy, 9-nonyleneoxycarbonyl, 8-octylenecarbonyloxy, 10-decyleneoxy, 10-decyleneoxycarbonyl, 9-nonylenecarbonyloxy, 11-undecyleneoxy, 11-undecyleneoxycarbonyl, 10-decylenecarbonyloxy, 12-dodecyleneoxy, 12-dodecyleneoxycarbonyl, 11-undecylenecarbonyloxy, 3-propyleneiminocarbonyl, 4-butyleneiminocarbonyl, 5-pentyleneiminocarbonyl, 6-hexyleneiminocarbonyl, 7-heptyleneiminocarbonyl, 8-octyleneiminocarbonyl, 9-nonyleneiminocarbonyl, 10-decylenelminocarbonyl, 11-undecyleneiminocarbonyl, 12-dodecyleneiminocarbonyl, 2-ethylenecarbonylimino, 3-propylenecarbonylimino, 4-butylenecarbonylimino, 5-pentylenecarbonylimino, 6-hexylenecarbonylimino, 7-heptylenecarbonylimino, 8-octylenecarbonylimino, 9-nonylenecarbonylimino, 10-decylenecarbonylimino, 11-undecylenecarbonylimino, 6-(3-propyleneiminocarbonyloxy)hexylene, 6-(3-propyleneoxy)hexylene, 6-(3-propyleneoxy)hexyleneoxy, 6-(3-propyleneiminocarbonyloxy)hexyleneoxy, 6-(3-propyleneiminocarbonyl)hexylene, 6-(3-propyleneiminocarbonyl)hexyleneoxy, 1,2-ethylenedioxy, 1,3-propylenedioxy, 1,4-butylenedioxy, 1,5-pentylenedioxy, 1,6-hexylenedioxy, 1,7-heptylenedioxy, 1,8-octylenedioxy, 1,9-nonylenedioxy, 1,10-decylenedioxy, 1,11-undecylenedioxy, 1,12-dodecylenedioxy and the like.
The aliphatic, alicyclic or aromatic divalent radical F is derivable from aliphatic, alicyclic or aromatic diamines by formal removal of the amino groups. Examples of aliphatic or alicyclic diamines from which the radical F can be derived include ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, 1,5-pentylenediamine, 1,6-hexylenediamine, 1,7-heptylenediamine, 1,8-octylenediamine, 1,9-nonylenediamine, 1,10-decylenediamine, 1,11-undecylenediamine, 1,12-dodecylenediamine, xcex1,xcex1xe2x80x2-diamino-m-xylene, xcex1,xcex1xe2x80x2-diamino-p-xylene, (5-amino2,2,4-trimethylcyclopentyl)methylamine, 1,2-diaminocyclohexane, 4,4xe2x80x2-diaminodicyclohexylmethane, 1,3-bis(methylamino;cyclohexane and 4,9-dioxadodecane-1,12-diamine.
Examples of aromatic diamines from which the radical F can be derived include 3,5-diaminobenzoic acid methyl ester, 3,5-diaminobenzoic acid hexyl ester, 3,5-diaminobenzoic acid dodecyl ester, 3,5-diaminobenzoic acid isopropyl ester, 4,4xe2x80x2-methylenedianiline, 4,4xe2x80x2-ethylenedianiline, 4,4xe2x80x2-diamino-3,3xe2x80x2-dimethyldiphenylmethane, 3,3xe2x80x2,5,5 xe2x80x2-tetramethylbenzidine, 4,4xe2x80x2-diaminodiphenyl sulfone, 4,4xe2x80x2-diaminodiphenyl ether, 1,5-diaminonaphthalene, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-diaminobiphenyl, 3,4xe2x80x2-diaminodiphenyl ether, 3,3xe2x80x2-diaminobenzophenone, 4,4xe2x80x2-diaminobenzophenone, 4,4xe2x80x2-diamino-2,2xe2x80x2-dimethylbibenzyl, bis[4-(4-aminophenoxy)phenyl]sulfone, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 2,7-diaminofluorene, 9,9-bis(4-aminophenyl)fluorene, 4,4xe2x80x2-methylenebis(2-chloroaniline), 4,4xe2x80x2-bis(4-aminophenoxy)biphenyl, 2,2xe2x80x2,5,5xe2x80x2-tetra-chloro-4,4xe2x80x2-diaminobiphenyl, 2,2xe2x80x2-dichloro4,4xe2x80x2-diamino-5,5xe2x80x2-dimethoxybiphenyl, 3,3xe2x80x2-dimethoxy-4,4xe2x80x2-diaminobiphenyl, 4,4xe2x80x2-(1,4-phenyleneisopropylidene)bisaniline, 4,4xe2x80x2-(1,3-phenyleneisopropylidene)bisaniline, 2,2-bis[4-(4-aminophenoxy)phenyl]-propane, 2,2-bis[3-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[3-amino-4-methylphenyl]hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2xe2x80x2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, 4,4xe2x80x2-di-amino-2,2xe2x80x2-bis(trifluoromethyl)biphenyl, and 4,4xe2x80x2-bis[(4-amino-2-trifluoromethyl)-phenoxy]-2,3,5,6,2xe2x80x2,3xe2x80x2,5xe2x80x2,6xe2x80x2-octafluorobiphenyl.
The group E may be divalent, trivalent or tetravalent. When E is divalent, it serves to link the groups S4 and S5, S6 and S7 or S8 and N respectively of the groups III to VII. It will be appreciated that when E is a divalent group, the monomer unit of which it forms a part is not linked to a side chain group of formula (I). When E is a trivalent or a tetravalent group, it serves to link the monomer unit, of which it forms a part, to one or two side chain groups of formula (I) respectively. It is preferred that the photoactive polymer comprises less than 75% of monomer units including a divalent group E, preferably less than 50% and especially less than 30%. Monomer units comprising a trivalent group E are preferred.
The building blocks of the formulae III, V and VII are amic acid groupings or amic acid ester groupings (i.e. carboxamide-carboxylic acid groupings or carboxamide-carboxylic acid ester groupings) which on the one hand may occur as a result of incomplete imidisation in the polyimide chain. On the other hand, polymers that consist only of building blocks of formulae III, V or VII, that is to say polyamic acids or polyamic acid esters, are important precursors for the preparation of the polyimides according to the invention and are also included in the present invention. Of those polymers which contain groups of formulae III, V or VII, preference is given to those in which G is hydrogen, that is to say those which consist exclusively of, or contain some, polyamic acid groups.
The polymers of the invention may be prepared using methods that are known to a person skilled in the art and a second aspect of the invention provides a method of preparing a compound of formula (I) as defined above.
Polyamic acids and polyimides of the present invention may be prepared in accordance with known methods, such as those described in Plast. Eng. 36 (1996) (Polyimides, fundamentals and applications).
For example, the polycondensation reaction for the preparation of the polyamic acids is carried out in solution in a polar aprotic organic solvent, such as xcex3-butyrolactone, N,N-dimethylacetamide, N-methylpyrrolidone or N,N-dimethylformamide. In most cases equimolar amounts of the dianhydride and the diamine are used, that is to say one amino group per anhydride group. If it is desired to stabilise the molecular weight of the polymer, it is possible for that purpose to add an excess or a less-than-stoichiometric amount of one of the two components or to add a monofunctional compound in the form of a dicarboxylic acid monoanhydride or in the form of a monoamine. Examples of such monofunctional compounds are maleic acid anhydride, phthalic acid anhydride, aniline and so on. The reaction is carried out preferably at a temperature of less than 100xc2x0 C.
The cyclisation of the polyamic acids to form the polyimides can be carried out by heating, that is to say by condensation with removal of water or by other imidisation reactions with reagents. When carried out purely thermally, the imidisation of the polyamic acids is not always complete, that is to say the resulting polyimides may still contain proportions of polyamic acid. The imidisation reactions are generally carried out at a temperature of from 60 to 250xc2x0 C., but preferably at less than 200xc2x0 C. In order to achieve imidisation at rather lower temperatures there are additionally mixed into the reaction mixture reagents that facilitate the removal of water. Such reagents are, for example, mixtures consisting of acid anhydrides, such as acetic acid anhydride, propionic acid anhydride, phthalic acid anhydride, trifluoroacetic acid anhydride, and tertiary amines, such as triethylamine, trimethylamine, tributylamine, pyridine, N,N-dimethylaniline, lutidine, collidine etc. The amount of reagents used in that case is preferably at least two equivalents of amine and four equivalents of acid anhydride per equivalent of polyamic acid to be condensed.
The imidisation reaction can be carried out before or alternatively only after application to a support. The latter variant is preferred especially when the polyimide in question has poor solubility in the customary solvents.
The polyamic acids and the polyimides of the present invention have an intrinsic viscosity preferably in range of 0.05 to 10 dL/g, more preferably 0.05 to 5 dL/g. Herein, the intrinsic viscosity (xcex7inb=1n xcex7rel/C.) is determined by measuring a solution containing a polymer in a concentration of 0.5 g/100 ml for its viscosity at 30xc2x0 C. using N-methyl-2-pyrrolidone as solvent.
The polyamic acid chains or polyimide chains of the present invention preferably contain from 2 to 2000 monomer units, especially from 3 to 200.
Additives such as silane-containing compounds and epoxy-containing crosslinking agents may be added to the polymers of the invention in order to improve the adhesion of the polymer to a substrate. Suitable silane-containing compounds are described in Plast. Eng. 36 (1996) (Polyimides, fundamentals and applications). Suitable epoxy-containing crosslinking agents include 4,4xe2x80x2-methylenebis(N,N-diglycidylaniline), trimethylolpropane triglycidyl ether, benzene-1,2,4,5-tetracarboxylic acid 1,2:4,5-N,Nxe2x80x2-diglycidyldiimide, polyethylene glycol diglycidyl ether, N,N-diglycidylcyclohexylamine and the like.
Further additives such as a photosensitiser, a photoradical generator and/or a cationic photoinitiator may also be added to the polymers of the invention. Suitable photoactive additives include 2,2-dimethoxyphenylethanone, a mixture of diphenylmethanone and N,N-dimethylbenzenamine or ethyl 4-(dimethylamino)benzoate, xanthone, thioxanthone, IRGACURE(trademark) 184, 369, 500, 651 and 907 (Ciba), Michler""s ketone, triaryl sulfonium salt and the like.
The polymers according to the invention may be used alone or in combination with other polymers, oligomers, monomers, photoactive polymers, photoactive oligomers and/or photoactive monomers, depending up on the application to which the polymer layer is to be put. It will therefore be appreciated that by varying the composition of the polymer layer it is possible to control properties such as an induced pretilt angle, good surface wetting, high voltage holding ratio, a specific anchoring energy etc.
Polymer layers may be readily prepared from the polymers of the present invention and a third aspect of the invention provides a polymer layer comprising a polymer according to the present invention in a crosslinked form. The polymer layer is preferably prepared by applying one or more polymers according to the invention to a support and, after any imidisation step which may be necessary, crosslinking the polymer or polymer mixture by irradiation with linearly polarised light. It is possible to vary the direction of orientation and the tilt angle within the polymer layer by controlling the direction of irradiation of the linearly polarised light. It will be appreciated that by selectively irradiating specific regions of the polymer layer it is possible to align very specific regions of the layer and provide layers with a defined angle of tilt. This orientation and tilt is retained in the polymer layer by the process of crosslinking.
It will be appreciated that the polymer layers of the present invention can also be used as orientation layers for liquid crystals and a preferred embodiment of the third aspect of the invention provides an orientation layer comprising one or more polymers according to the invention in a crosslinked form. Such orientation layers can be used in the manufacture of optical constructional elements, preferably in the production of hybrid layer elements.
The orientation layers are suitably prepared from a solution of the polymer material. The polymer solution is applied to a support optionally provided with an electrode (for example a glass plate coated with indium-tin oxide (ITO)) by a spin coating process, to produce homogeneous layers of 0.05 to 50 xcexcm thickness. For applying the polymer material, generally different coating techniques may be used like spincoating, miniscuscoating, wirecoating, slotcoating, offsetprinting, flexoprinting, and gravurprinting.
The resulting layer is imidised, if required, and may then be selectively orientated by irradiation with a high-pressure mercury vapour lamp, a xenon lamp or a pulsed UV laser, using a polariser and optionally a mask for creating images of structures. The irradiation time is dependent upon the output of the individual lamps and can vary from a few seconds to several hours. The crosslinking reaction can also be carried out by irradiation using filters that, for example, only allow the radiation suitable for the crosslinking reaction to pass through.
It will be appreciated that the polymer layers of the invention may be used in the production of optical or electro-optical devices having at least one orientation layer as well as unstructured and structured optical elements and multi-layer systems; especially for use in vertical aligned nematic (VAN) LCDs and hybrid aligned nematic (HAN) LCDs.
A further embodiment of the third aspect of the invention provides an optical or electro-optical device comprising one or more polymers according to the first aspect of the invention in crosslinked form. The electro-optical devices may comprise more than one layer. The or each of the orientation layers may contain one or more regions of different spatial orientation.
The polymers in accordance with the invention are illustrated in more detail by the following Examples.